Download the twinQ2 manual

2
TM
150
200
PAD
50
40
LINE
twin
0
-3
Hz
3k
+9
dB
LF FREQ
+12
+15
0
-3
2k
1k
+6
-12
-15
650
1k5
+3
-6
400
-9
85
+3
-6
-3
+6
-9
0
+3
-6
+9
-9
4k
300
5k
Hz
-15
+15
dB
-15
MID
2
35(0)
40 PEAK
25
45
20
INSTR
dB
0
48V
150
dB
+15
0
-4
3:1
-10
+4
VU
dB
PAD
+10
40
LINE
M E E K
GAIN
10
+10
+8
1
50
+5
+12
GAIN
-20
+3
COMPRESS
HPF
1:1
10:1
SLOPE
1
ms
100
ATTACK
0.1
sec
dB
LF FREQ
1
GR
+12
+15
3
RELEASE
+3
-6
-3
+6
-9
+16
0
dB
30
COMP
+9
300
INSTR
PRE
GR
40 PEAK
45
CLK
LINK
dB
-20 -10
+4
-7 -5 -3
-15
MID FREQ
0
-4
+15
dB
-15
MID
3:1
-10
+4
dB
-oo
+15
dB
+3
DUAL STUDIO
CHANNEL
+10
M E E K
GAIN
HF (12kHz)
ON
10
J O E M E E K
0.3
+8
5:1
2:1
5
+10
0
VU
-30
5k
Hz
PEAK
FSD
0
-20
+9
1
50
-15
+5
+12
+3
2
GR
+16
METER
2
50
18
EXT
ON
-9
-6
-10
-15
+6
OPTICAL COMPRESSOR
35(0)
20
+20
MAKE UP
GAIN
+3
4k
LF
25
METER
0
-6
6kHz
/
O
2
dBu
-12
-15
650
3k
+9
0
-3
2k
1k
+6
PREAMP
-15
+oo
60
Hz
1k5
+3
IRON
0.3
5
0
-3
-6
400
-9
85
ON
5:1
2:1
200
+3
50
HF (12kHz)
50
18
-7 -5 -3
OPTICAL COMPRESSOR
PREAMP
30
+4
-oo
6kHz
IRON
/
O
-20 -10
-30
MID FREQ
LF
0
-20
+9
OUTPUT
MEEQUALIZER
PEAK
FSD
-6
-10
-15
+6
+oo
60
GAIN
dBu
-20
1:1
COMPRESS
SLOPE
HPF
twinQ2
Dual Studio Channel
User Guide
joemeek.com
10:1
1
ms
100
ATTACK
0.1
sec
3
RELEASE
0
dB
+20
MAKE UP
GAIN
O
OUTPUT
MEEQUALIZER
48V
ON
PRE
GR
TM
Designed in England and
assembled in China
to strict Joemeek specifications,
Joemeek is manufactured under the direction
of and distributed exclusively by:
PMI AUDIO GROUP
USA: 1845 W. 169th Street
Gardena, CA 90247
toll free: 877-563-6335
fax: 310-323-0900
UK: Unit 4 Minerva Court
Woodland Industrial Estate
Torquay, TQ2 7BD
tel: +44 (0)1803-612700
fax: +44 (0)1803-612009
email: [email protected]
www.joemeek.com
Written by Allan Bradford, MSc
JOEMEEK ®
is a registered trademark of PMI Audio Group
Important Safety Instructions
Important Safety Information
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water. Do not expose to
drips or splashes. Do not place any objects filled with
liquids, such as vases, on the apparatus.
6. Clean only with dry cloth.
7. Do not block any ventilation openings. Do not install this
apparatus in a confined space such as a book case or
similar unit. Install only in racks designed for the purpose
and in accordance with manufacturers’ instructions.
8. Do not install near any heat sources such as radiators,
heat registers, stoves, or other apparatus (including
amplifiers) that produce heat.
9. Do not defeat the safety purpose of the polarized or
grounding-type plug. A polarized plug has two blades with
one wider than the other. A grounding-type plug has two
blades and a third grounding prong. The wide blade or the
third prong are provided for your safety. If the provided
plug does not fit into your outlet, consult an electrician for
replacement of the obsolete outlet.
10. Protect the power cord from being walked on or
pinched particularly at plugs, convenience receptacles,
and the point where they exit from the apparatus.
11. Only use attachments and accessories specified by
the manufacturer.
CAUTION
CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK,
DO NOT REMOVE COVER. NO USER-SERVICEABLE PARTS
INSIDE. REFER SERVICING TO QUALIFIED SERVICE
PERSONNEL.
The lightning flash with arrowhead symbol, within an
equilateral triangle, is intended to alert the user to the
presence of uninsulated “dangerous voltage” within the
product’s enclosure that may be of sufficient magnitude
to constitute a risk of electric shock to persons.
The exclamation point within an equilateral triangle is
intended to alert the user to the presence of important
operating and maintenance (servicing) instructions in
the literature accompanying the appliance.
WARNING: TO AVOID FIRE OR ELECTRIC
SHOCK HAZARD, DO NOT EXPOSE THIS
APPARATUS TO WATER, RAIN OR MOISTURE.
NOTE — This apparatus does not exceed the Class
A/Class B (whichever is applicable) limits for radio noise
emissions from digital apparatus as set out in the radio
interference regulations of the Canadian Department of
Communications.
.
ATTENTION — Le présent appareil numérique n’émet
pas de bruits radioélectriques dépassant las limites
applicables aux appareils numériques de class A/de class
B (selon le cas) prescrites dans le réglement sur le
brouillage radioélectrique édicté par les ministere des
communications du Canada.
These limits are designed to provide reasonable
protection against harmful interference in a
commercial/residential installation respectively. This
equipment generates, uses, and can radiate radio
frequency energy and, if not installed and used in
accordance with the instruction manual, may cause
harmful interference to radio communications. There is
no guarantee that interference will not occur in a particular
installation. If this equipment does cause interference to
radio or television equipment reception, which can be
determined by turning the equipment off and on, the user
is encouraged to try to correct the interference by any
combination of the following measures: (1) Relocate or
reorient the receiving antenna (2) Increase the separation
between the equipment and the receiver (3) Plug the
equipment into an outlet on a circuit different from that to
which the receiver is connected (4) Consult your dealer or
experienced radio/television technician for additional
assistance.
12. Use only with a cart, stand, tripod, bracket, or table
specified by the manufacturer, or sold with the apparatus.
When a cart is used, use caution when moving the
cart/apparatus combination to avoid injury from tip-over.
13. Unplug this apparatus during lightning storms or when
unused for long periods of time.
14. Refer all servicing to qualified service personnel.
Servicing is required when the apparatus has been
damaged in any way, such as power-supply cord or plug
is damaged, liquid has been spilled or objects have fallen
into the apparatus, the apparatus has been exposed to
rain or moisture, does not operate normally, or has been
dropped.
15. Apparatus designed with Class-I construction must be
connected to a mains socket outlet with a protective
earthing connection (the third grounding prong).
16. This apparatus may be equipped with a single-pole,
rocker-style AC mains power switch. If so this switch is
located on the front panel and should remain readily
accessible to the user.
17. The manufacturer reserves the right to change the
technical specification of the product without prior notice.
CAUTION — Changes or modifications to this equipment
not expressly approved by the party responsible for
compliance could void the user's authority to operate this
equipment.
3
Statement of RoHS Compliance
Statement of WEEE Policy
PMI Audio Group manufactures complete electronic
products which are covered by the European Union’s
“Removal of Hazardous Substances” directive
2002/95/EC (RoHS). This directive seeks to eliminate
toxic substances from the manufacturing process, such
that when equipment is disposed of at the end of its life
cycle, the materials it contains do not contaminate the
environment and pose health risks. Banned substances
are lead, mercury, cadmium, hexavalent chromium,
polybrominated biphenyls (PBB) and poly-brominated
diphenyl ethers (PBDE). Lead is used together with tin in
solder connections to reduce the melting point of solder.
Lead-free solder requires higher soldering temperatures
which in turn places greater thermal stress on
components.
PMI Audio Group manufactures many complete
electronic products which are covered by the European
Union’s “Waste Electric and Electronic Equipment”
directive 2002/96/EC (WEEE). This directive seeks to
ensure that waste electric and electronic equipment is
disposed of in an environmentally responsible manner, at
the end of its life cycle. PMI Audio Group takes seriously
its obligations under this directive to take back WEEEaffected products and, from 13th August 2005, will mark
all such products with the crossed-out wheeled bin
symbol.
RoHS
COMPLIANT
Business to Business products: PMI Audio Group will
cost-neutrally take back WEEE-affected electric and
electronic equipment in this category, from 1st January
2006. PMI Audio Group will work with disposal and
recycling partners working within the EU. The waste
electric and electronic equipment can then be turned over
to a disposal and recycling companies in the countries
concerned.
Business to Customer products: emerging electric and
electronic equipment will be disposed of by local
authorities' collection systems.
Dual Use products: this equipment will be disposed of by
local authorities' collection systems.
Pb
PMI Audio Group takes seriously its obligations under the
RoHS directive and insists that its factories use only
components that are certified RoHS compliant, as well as
lead-free solder. In a very few cases the necessary
components may not yet be available to the world market
but we work continuously to eliminate any such
exceptions at the earliest opportunity. Our printed Circuit
Boards (PCB’s) and all soldered joints have been leadfree since 2005.
4
Contents
JOEMEEK: the Legend Continues
Controls at a Glance..........................................6 & 7
Joemeek studio processors represent a quantum leap in the
history of the Joemeek legend. Long regarded for its "Big
Sound", the original Joemeek gear was both revered and
reviled for its somewhat "quirky" nature. So we took the best
of what made the old Joemeek products sound great, refined
it, distilled it, added to it and repackaged it.
Overview..............................................................5
Preamplifier.........................................................8
Insert Point..............................................................9
Meter......................................................................9
Compressor............................................................9
Meequalizer............................................................11
Output Stage..........................................................12
Digital Interface.......................................................12
Properly and robustly engineered for predictable,
controllable performance, the latest generation retains the
famous Joemeek sound, with its wide, flat frequency
response extending from subsonic to ultrasonic. It also uses
genuinely low noise circuitry, with lots of headroom
(immunity to overload). Accurate calibration and metering,
together with clear panel labeling, give you complete
confidence in what's going on. Joemeek products are
founded on good solid electronic and audio engineering, and
withstand direct comparison with the very best names in
mixers and outboard gear.
Using the twinQ2...................................................13
Getting Connected..................................................13
Using the Preamp...................................................13
Using the Compressor.............................................13
Using the Meequalizer.............................................13
Using the Output Stage...........................................14
The Joemeek range provides everything you need to get
your performance into your recording device.
Now the latest JOEMEEK Q2 series features an entirely new
world-class Preamp using a top-quality Cinemag
microphone transformer. In addition, low noise Burr Brown
OPA2134 audio amplifiers are used throughout the signal
path, headroom is increased and power consumption is
reduced.
Troubleshooting...................................................14
Technical Specification........................................15
Overview
About the Designer
The JOEMEEK twinQ2 is like having one channel of a
professional recording studio in one box. It takes
microphones or instruments, amplifies them, compresses
and equalises them ready to be recorded. Simple to use yet
extremely powerful, the twinQ2 will bring out the best in any
microphone or instrument and give the gloss of a
professional studio production to all your performances. It
can also be very useful for live work!
Since 2003 the Joemeek product range has been designed
by renowned audio electronics engineer Allan Bradford. With
his background in physics and over 30 years experience with
the design of instruments, mixers, processors and amplifiers,
Allan's unique range of expertise ensures that Joemeek
remains at the forefront of music technology.
Think of the twinQ2 as five separate items of equipment:
• Preamplifier
• JOEMEEK Optical Compressor
• Meequalizer EQ
• Fader
• A to D Converter
... twice!
5
Controls at a Glance
150
200
85
PAD
50
40
LINE
twin
0
-3
Hz
3k
+9
dB
LF FREQ
+12
+15
0
-3
2k
1k
+6
-12
-15
650
1k5
+3
-6
400
-9
+3
-6
0
-3
+6
-9
+3
-6
+9
-9
4k
300
5k
Hz
-15
+15
dB
-15
MID
2
35(0)
40 PEAK
25
45
20
dB
INSTR
dB
0
48V
150
0
-4
3:1
-10
+4
VU
dB
PAD
+10
40
LINE
M E E K
GAIN
10
+10
+8
1
50
+5
+12
GAIN
-20
+3
COMPRESS
1:1
10:1
SLOPE
1
ms
100
ATTACK
0.1
sec
3
RELEASE
HPF
dB
LF FREQ
1
GR
+12
+15
+3
-6
-3
+6
-9
+16
0
dB
30
COMP
+9
300
INSTR
PRE
GR
40 PEAK
45
CLK
LINK
dB
-20 -10
+4
-7 -5 -3
0
-15
MID FREQ
0
-4
+15
dB
-15
MID
3:1
-10
+4
dB
-oo
+15
dB
DUAL STUDIO
CHANNEL
+10
M E E K
GAIN
HF (12kHz)
ON
10
J O E M E E K
0.3
+8
5:1
2:1
5
+10
+3
VU
-30
5k
Hz
0
-20
+9
1
50
-15
+5
+12
+3
2
GR
+16
METER
2
50
18
EXT
ON
-9
PEAK
FSD
-6
-10
-15
+6
OPTICAL COMPRESSOR
35(0)
20
+20
MAKE UP
GAIN
+3
4k
LF
25
METER
0
-6
6kHz
/
O
2
dBu
-12
-15
650
3k
+9
0
-3
2k
1k
+6
PREAMP
-15
+oo
60
Hz
1k5
+3
IRON
0.3
5
0
-3
-6
400
-9
85
ON
5:1
2:1
200
+3
50
-oo
+15
50
18
-7 -5 -3
OPTICAL COMPRESSOR
PREAMP
30
+4
HF (12kHz)
6kHz
IRON
/
O
-20 -10
-30
MID FREQ
LF
0
-20
+9
OUTPUT
MEEQUALIZER
PEAK
FSD
-6
-10
-15
+6
+oo
60
GAIN
dBu
-20
COMPRESS
HPF
1:1
10:1
SLOPE
1
ms
100
ATTACK
0.1
sec
3
RELEASE
0
dB
+20
MAKE UP
GAIN
O
OUTPUT
MEEQUALIZER
48V
ON
PRE
GR
48V PHANTOM POWER switch - feeds 48 volts to the
microphone XLR connectors, to power condenser microphones.
MAKE UP GAIN - restores the level of the signal after
compression.
PAD switch - selects 20dB attenuation of the Mic (XLR) inputs.
COMP LINK - for stereo work, the master twinQ2's "Compress",
"Attack" and "Release" control both master and slave twinQ2 (the
corresponding controls on the slave twinQ2 are redundant). This
avoids stereo image shifts. All other controls still operate
independently on both master and slave and must be set the
same for correct stereo balance.
LINE switch - selects the Line and INSTRument (1/4" jack)
inputs and deselects the Mic (XLR) input.
IRON switch - selects transformer coupling of the Line (1/4" jack)
inputs.
Ø switch - reverses the phase of all inputs.
Compressor ON switch - turns the compressor on.
MIC input - low impedance microphone input. Parallels the Rear
Panel MIC socket. Use only one of these two sockets at a time.
LF - controls the volume of Low Frequencies or "Bass" in the
audio spectrum. 15dB of boost or cut is available at the selected
frequency.
INSTRument input - high impedance input. Plugging in here
overrides anything plugged into the Line or Mic inputs.
LF FREQ - sets the frequency at which the LF control operates,
anywhere from 40Hz to 650Hz.
PREAMP GAIN - sets the amount of audio amplification. Too little
gain and the sound will be too quiet; too much and the signal
could become distorted.
PEAK LED - lights 6dB below clipping.
MID - controls the Higher Middle frequencies in the audio
spectrum. 15dB of boost or cut is available at the selected
frequency.
HPF - "high-pass filter". Mainly for use with microphones, this
helps remove stage rumble, handling noise and "pops".
MID FREQ - sets the frequency at which the HM control operates,
anywhere from 300Hz to 5kHz.
METER - analogue movement shows output signal level (VU),
preamp signal level, or the amount of Compressor gain reduction
(GR) in dB, depending on the settings of the Meter switches. The
'PRE' switch overrides both "VU" and "GR" metering.
HF - controls the volume of the High Frequencies or "Treble" in
the audio spectrum. 15dB of boost or cut is available at the
selected frequency.
6kHz switch - sets the frequency at which the HF control
operates: in for 6kHz, out for 12KHz.
COMPRESS - sets the level of signal (or "Threshold") above
which the signal starts to be compressed.
EQ ON switch - turns the Meequalizer on.
SLOPE - sets the compression ratio applied to signals above
threshold.
OUTPUT GAIN - the volume control or "Fader" for the output of
the twinQ2.
ATTACK - sets how quickly the compressor responds to peaks
above threshold.
PEAK FSD LED - lights 6dB below clipping. "FSD" means "Full
Scale Digital" and this LED also warns you if the Digital Interface
is about to be overloaded.
RELEASE - sets the time taken for the signal to return to its
normal size after compression. In general, the longer the time,
the less obvious the compression.
'EXT CLK' LED - illuminates when the twinQ2's digital output is
successfully locked to an external word clock
6
Rear Panel at a Glance
twinQ 2 DUAL STUDIO CHANNEL
CAUTION
AC POWER ONLY
VOLTAGE: 115/230 V~
FREQUENCY: 50/60 Hz
POWER: 30 VA
J O E M E E K
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
CAUTION
ENSURE CORRECT RATINGS
WHEN REPLACING FUSES.
FUSE RATINGS:
230V~ T500mA
115V~ T1A
EN55103
EN60065
www.joemeek.com
DESIGNED IN THE UK FOR PMI AUDIO
MADE IN CHINA
ENSURE MAINS VOLTAGE AND FUSE RATINGS
ARE CORRECT BEFORE CONNECTING MAINS POWER.
THIS APPARATUS MUST BE EARTHED BY THE POWER CORD.
NO USER SERVICEABLE PARTS REFER SERVICING TO QUALIFIED PERSONNEL.
CHANNEL 2
CHANNEL 1
DIGITAL INTERFACE
AES/EBU
OUTPUT
SPDIF
OUTPUT
OPTICAL
OUTPUT
WORD
CLOCK IN
48k
x2
+4dBu
+4dBu
44.1k
x1
-10dBV
-10dBV
SAMPLE
FREQUENCY
OUTPUT
+4dBu OUTPUT
DIGITAL INTERFACE - outputs two channel digital audio in
S/PDIF format (optical and RCA phono connectors) and AES3
(XLR connector).
INSERT
LINE INPUT
MIC INPUT
OUTPUT
+4dBu OUTPUT
INSERT
LINE INPUT
MIC INPUT
+4dBu/-10dBv switch - selects the operating level of the 1/4"
jack output, either to the professional standard of +4dBu, or to
-10dBv which may be more suitable for hi-fi amplifiers and some
computer sound cards.
WORD CLOCK INPUT - BNC connector allows the twinQ2 to be
synchronized to an external word clock.
Sample Rate switches - select 44.1kHz, 48kHz, 88.2kHz or
96kHz.
Channel 2 Analog Input - allows an external balanced analogue
audio signal to be fed to (the otherwise unused) digital channel 2.
7
Preamplifier
This is the all-important front end to the twinQ2. Its job is to accept
any type of microphone, instrument or other source of audio
signal, and make it loud enough. Microphones need rather a lot of
amplification, while guitars, keyboards and CD players need less.
Mics need to be connected to low impedance inputs, while
instruments prefer high impedance inputs. To ensure correct
impedance matching, the inputs are split into an XLR connector
for Mics, and 1/4" jack "Line" and "INSTRument" connectors for
everything else. A switch on the front panel decides which input
connector is active, the XLRs or the 1/4" jacks. The LED next to
the switch lights to show that the Line inputs (jacks) are selected:-
Microphone inputs up to +4dBu can be accommodated without
distortion (+24dBu by using the 'PAD' switch).
The (0) symbol next to the 35dB mark, means unity gain, or 0dB,
for a signal in the Line input. For Line inputs the range of gain
adjustment either side of this mark, is +22dB, -19dB. For the
"INSTRument" input the gain range is 0dB to +40dB.
The microphone input transformer is permanently assigned to
the "Mic" Input. The 'IRON' switch optionally sends the "Line"
input through the transformer, to add some colouration to Line
sources.
The 'PEAK' LED lights +16dBu, which is 6dB below clipping, so
occasional brief flashes are OK but if it's on all the time you need
to back off the Input Gain!
'LINE' switch out (LED off) = "Mic"
'LINE' switch in (LED on) = "Line" or "Instr"
The Mic input is transformer balanced and the Line input is
electronically balanced. Note: although the Line input is not
normally used for microphones, it can also be suitable for some
high output unbalanced microphones, such as battery powered
Electret types. The front and rear panel Mic inputs (XLR) are
balanced and wired as follows:
'HPF' means "high-pass filter". Mainly for use with microphones,
this helps remove stage rumble, handling noise and "pops". The
LED lights when active.
Technical stuff
Very low noise - does it matter? Yes and no, it all depends what
you are doing - what really matters is "signal-to-noise ratio". All
electronics produce a certain amount of background noise - it's in
the nature of things. Providing there is only a relatively small
amount of noise, the signal will cover it up, or "mask" it. So
providing the signal is much bigger than the noise, you won't be
aware of the noise. In other words the "signal-to-noise ratio"
needs to be a big number, ideally such as 80dB or 90dB.
Pin 2: + (hot)
Pin 3: - (cold)
Pin 1: ground
The Line input (jack) is balanced and wired as follows:
Tip: + (hot)
Ring: - (cold)
Sleeve: ground
So how do you achieve that in practice? The trick is to keep the
microphone as close to the sound source as possible without
overloading it, so as to get as much signal out of it as possible.
Then you set the Gain control to give only as much gain as is
needed to get a decent level into the recorder.
The front panel Instrument jack is balanced and wired as follows:
Tip: + (hot)
Sleeve: ground (NB: use a mono jack plug).
Note that if something is plugged into the Instrument input,
anything plugged into the rear panel Line input will be cut off.
Of course when there is no signal going on, you may hear the
background noise of the electronics. In that case, given the
amount of gain in a typical studio monitoring system, this noise
"floor" should ideally be in the region of -80dBu or lower, in order
for it not to be noticed.
Phantom power
Most high-quality studio mics are "Phantom Powered", which is
to say they have electronics inside them, which get their power
from the preamp. Most mics require a supply of 48 volts, so
Phantom Power is often labelled "48V". The '48V' switch turns
this power on and a red LED lights when active. When switching
the Phantom Power on, quite a loud thump may be produced, so
it is a good idea to turn down the Output Gain (or to momentarily
select the Line input), when pressing the '48V' switch.
The twinQ2 microphone preamplifier uses state-of-the-art
electronics and has an equivalent input noise of around -127dBu
(with a 150ohm input load). Despite all the hyperbolae and
obfuscation, the theoretical best possible performance with
silicon-based electronics is about -131dBu. So the preamplifier
used in the twinQ2 and all other Joemeek products approaches
this limit. To improve significantly on this would require highly
specialised electronics and probably a vat of liquid Nitrogen to
cool it!
When using dynamic or older ribbon mics, do not turn Phantom
Power on. It probably won't do any harm but it certainly won't do
any good, so leave it off! Consult the microphone handbook if you
are unsure what kind of mic you have.
The maximum gain available from the preamp is 60dB, in which
case the noise floor will be -67dBu. This is actually quite noisy - if
you record that noise onto a digital recorder and play it back you
will definitely hear it. In practice of course, you do not record and
play back "silence" and the rest of the mix will probably be more
than 70dB louder than this noise and will mask it completely. Even
so it is generally a good idea not to use gains greater than 40dB or
50dB and indeed, it should rarely be necessary to do so.
The main control, labelled 'INPUT GAIN', covers a range of
microphone amplification from 18dB to 60dB. In many other
preamps the action of the "Gain" control is rather uneven, with the
40dB to 60dB range being crammed into the last 1/6th of a turn.
All Joemeek preamps use a specially designed control that
ensures smooth operation over the whole range of rotation, with
extra sensitivity in the crucial 25dB to 45 dB range.
8
Insert Point
Compressor
This is simply an unbalanced "Send and Return" jack on the rear
panel. It allows you to patch any other pieces of equipment into
the signal path, such as an effects processor or noise gate. To use
it you will need a "Y" lead wired as follows:
The hardest device to understand, yet one of the most useful, the
PhotoOptical Compressor is what gives Joemeek products their
unique character. Its job is to make quiet sounds louder and loud
sounds quieter, or in other words to reduce the dynamic range of
the programme material. It's a bit like manually riding the volume
control, except the compressor does it automatically, responding
far quicker and more accurately than you ever could by hand. The
compressor is applied in several ways:
Tip: send
Ring: return
Sleeve: ground
1. Make Sounds Stand Out
When no jack is inserted, the socket is internally linked, or
"normalled", so that the signal flows uninterrupted. Note that the
Insert Point is after the Preamp in the signal path but before the
Compressor and Meequalizer.
Because compressors make loud sounds quieter, you can boost
the volume of the quiet bits without the loud bits getting even
louder. That means you can raise the average level of an
instrument or vocal in the mix, which has the effect of lifting it and
bringing it forwards. This can actually improve vocals for
example, bringing them out in front of a mix, making them sound
denser, more even, and more confident!
Meter
The analogue meter displays one of three things, depending on
the setting of the "VU Meter" switches.
2. Crank Up The Volume
Raising the average volume of whole mixes means they can be
heard in noisy environments, such as vehicles and factories.
Boosting the average level is what makes radio stations sound
LOUD and the same technique is used on TV commercials too,
which is why they always seem annoyingly louder than the movie
you were trying to watch!
In VU mode ('PRE' switch out), the Meter shows the signal level at
the XLR Output, after the 'OUTPUT GAIN' fader. Note that this is
relative to the operating level of "+4dBu", so if the meter reads "0",
then you will have +4dBu coming out of the XLR.
(In the case of the 1/4" jack output socket, if you have selected
"+4dBu" using the Rear Panel switch and the meter reads "0",
then you will have +4dBu coming out of the jack socket. If you
have selected "-10dBv" using the Rear Panel switch and the
meter reads "0", then you will have -10dBv coming out of the
output jack).
3. Protection
Fast response times are generally used to control brief transients.
In other words if an occasional peak sticks its head above a
maximum permitted level, the compressor clobbers it; this is
known as limiting and a compressor designed solely for this
purpose is known as a Limiter. Limiters are primarily used to
protect recorders and monitor systems from overload, radio
transmitters from overmodulation, etc. The Joemeek compressor
is not primarily intended for this purpose as the Attack is not really
fast enough to satisfy radio station requirements, although it is
generally good enough to protect recorders and monitors, where
the effect of transients is less critical. Normally you should not
hear a limiter operating but if it is driven hard constantly, it can
render a mix somewhat flat and lifeless.
In Gain Reduction mode ('GR' switch in), the Meter changes to
read "0"dB, when no signal is present. Whenever the compressor
reduces the gain of a signal, the meter then moves "backwards"
to show the amount of gain reduction taking place at any moment.
Note that unlike many other products, in the twinQ2 this reading is
a true measurement of gain reduction, derived by comparing the
input and output of the PhotoOptical gain cell.
The third mode "PRE" allows the output of the preamp to be
metered directly, rather like the "PFL" button on a mixing console.
This is useful for adjusting the gain of the Preamp. The 'PRE'
switch overrides both "VU" and "GR" metering.
4. Accommodation
The dynamic range of the human ear is phenomenal, extending
from the threshold of hearing (eg: a pin dropping onto soft carpet)
to threshold of pain (eg: standing next to a jet aircraft) - some
120dBA in all. By contrast, vinyl, cassette tape and radio
broadcasts all have a dynamic range of about half that. Since the
advent of the CD, the dynamic range of the medium is far less of
an issue and compressors are used more to give a certain "feel"
to a production. AM and FM radio however, is still very much
compressed to fit its restricted dynamic range.
5. Modification
A compressor can change the dynamics, or "envelope" of the
track and it is here that the Joemeek Compressor excels!
9
Compressor (Cont'd)
Types of Compressor
'ATTACK' sets how quickly the compressor reacts to peaks
above threshold. Turn this control anticlockwise for a quick
response. Slower (clockwise) allows the fast leading edge of
percussive sounds to pass uncompressed for a moment, before
the compressor reacts to control the gain. This example of
"changing the envelope" of a sound exaggerates the percussive
nature of drums and other instruments. Settings around
mid-position are used where the compression needs to be less
obvious. Vocals for example, require Attack times around
10msec for natural sounding results. Faster attack times (anticlockwise) in conjunction with large amounts of compression,
result in extreme "pumping" effects.
Most compressors work in essentially the same way: a volumecontrolling element or "gain cell" is inserted into the audio signal
path. The level of the signal at any given moment is measured
and that information is used to control the gain cell. So if the signal
gets bigger, the volume is turned down. Various types of gain cell
in common use include FETs, valves (tubes), light-dependentresistors (photoelectric), digital potentiometers and voltagecontrolled-amplifiers, better known as VCAs.
The twinQ2 Compressor is a unique recreation of the sort of
photoelectric compressor used by record producer Joe Meek in
the 1960's. Using modern components for consistency and
reliability, it nonetheless reproduces faithfully the same punchy
sound that was so characteristic of the pop records of that time.
'RELEASE' sets how long the compressor goes on squashing
the sound for, once the signal has dropped below threshold. If it
stopped instantly there would be very noticeable modulation or
"pumping" of the sound. So we may want it to stop compressing
less abruptly and that is what the Release control is for. Generally,
the longer the Release time, the less obvious is the compression.
Of course some "pumping" might actually be desirable as a
special effect and that is another way in which the envelope of a
sound can be modified. The twinQ2 Release is variable from
100msec up to 3 seconds giving a wide variety of effects.
Compression Ratio
What?? OK, it's simpler than it sounds. If the input gets 10dB
louder but the output only increases by 5dB then the compression
ratio is "2 to 1". If the input goes up 10dB but the output only goes
up 1dB, then the compression ratio is "10 to 1". In a theoretically
ideal compressor, this ratio is the same for any size of signal
above the threshold but for that to be true, the gain cell and its
control circuitry must be perfectly linear over a very wide range. In
practice only compressors based on VCAs and digital
potentiometers are likely to behave in this way.
How the compressor behaves actually changes with programme
content and volume. So experiment with the controls with
different kinds of material to discover the range and depth of
effects that can be achieved. The 'COMP' in/out switch allows
comparison between compressed and uncompressed sound
(blue LED lights when active). Remember that the 'MAKE UP
GAIN' is there to restore the level of the signal after compression.
Correctly adjusted, there will be no change in volume as the
Compressor 'ON' switch is operated.
Some compressors have a control to set the ratio anywhere
between 1:1 (ie: no compression), and 20:1 (which would be
regarded as a "brick wall limiter"). In the twinQ2 the "Slope" or
"Compression Ratio" is variable from 1:1 (ie: no compression) to
10:1. Slopes around 3:1 are gentle for vocals while higher slopes
are hard for drums and guitars. However that's not all there is to it.
The Compressor is after the Preamplifier and the Insert Point,
and before the Meequalizer.
Variable Ratio
In the Joemeek optical compressor the compression 'threshold'
is not clearly defined and the compression ratio varies with the
amount of compression applied. Suppose the 'SLOPE' control is
set to 5:1. For signals only just exceeding threshold, the ratio is
little more than 1:1. As the compressor is driven harder, the ratio
rises to 5:1, at least up to a point. It is a feature of the Joemeek
compressor that the compression ratio actually reduces again
during large transients and, adjusted correctly, this helps to retain
brightness that is often lost with other types of compressor. This is
why vintage optical compressors often sound more lively than
their modern counterparts.
'COMP LINK'
This is important when the twinQ2 is used for stereo work. When
two mono compressors are used for stereo, differing amounts of
gain reduction occur in each channel, which causes the stereo
image to wander. The 'COMP LINK' switch avoids this problem by
summing the compressor control paths of both channels and
assigning control of ("slave") channel 2's gain cell to ("master")
Channel 1. The 'COMPRESS', 'ATTACK' and 'RELEASE'
controls on the Channel 1 then operate both channels and the
corresponding controls on Channel 2 are redundant. Note
however that all other controls still operate independently on both
channels and must be set the same for correct stereo balance.
The LED lights when active.
Controls
'COMPRESS' sets the level of signal (the "Threshold") above
which the signal starts to be compressed. Turning the
compression control clockwise lowers the compression
threshold, and drives the compressor harder.
'SLOPE' sets the average compression ratio applied to signals
above threshold. Lower settings (anti-clockwise) have less effect.
Turning the control clockwise increases the ratio and makes the
effects of compression more dramatic. At maximum (10:1) the
Joemeek compressor effectively becomes a limiter.
10
Meequalizer
The twinQ2 "Meequalizer" is a highly effective, versatile and
musically rewarding three-band equalizer, or tone control
system. Each stage allows boost or cut of up to 15dB around the
frequency in question. The 'EQ' switch turns the equalizer on, and
the green LED lights when active.
The LF band can be tuned or "swept" anywhere between 40Hz
and 650Hz. It may help to think of it as like a graphic equalizer,
only instead of lots of frequency bands, you have just one, but it
can be moved to cover any given frequency band. Cutting low
frequencies can be used to reduce unwanted low frequency
noise, such as hum or rumble. Boosting can bring out the warmth
and body of bass lines and (especially around 80Hz) kick drums.
Higher up, cutting can reduce boominess or other annoying
resonances, while boosting can bring out the body and warmth of
a vocal, or the harmonics of bass instruments.
LF and HF frequency response
The MID band can be tuned or "swept" anywhere between 300Hz
and 5kHz. Cutting higher MID frequencies can reduce sibilance
or other annoying resonances. Boosting can bring out the
harmonics of instruments or make vocals more distinct.
Increasing or reducing the "presence" of an instrument or vocal in
this way, can appear to move the sound forwards or backwards in
a mix.
The HF or treble section is centred at either 6kHz or 12kHz.
Boosting the 12kHz band gives a sense of "air" or "sparkle" to
vocals, instruments and mixes, without boosting harsh upper-mid
frequencies. Alternatively with bass instruments, cutting this
band will reduce HF noise such as hiss and crackle. The 6kHz
setting is very effective at controlling sibilance and reducing
harshness, or indeed creating it, for example by boosting the
harmonics of electric guitars.
Mid frequency response (at 300Hz and 5kHz)
The EQ 'ON' switch allows comparison between equalized and
unequalized sound (LED lights when the Meequalizer is active).
The Meequalizer is after the Preamplifier, the Insert Point and the
Compressor.
Technical stuff
Each section of the Meequalizer has a peaking or "bell" shaped
frequency response, which will be found to be musically more
satisfying than conventional "shelving" equalizers. The use of bell
curves at LF and HF also avoids boosting subsonics and
ultrasonics which can have adverse effects on other studio
equipment, such as recorders, monitor amplifiers and speakers.
The "Q" value of the peaking filters is 0.9 (or 1.6 octaves). Zero
phase distortion ensures the best possible audio coherence.
11
Output Stage
Digital Interface
'OUTPUT GAIN'. This output volume control provides up to 10dB
of gain and also goes right down to nothing, so acting as a fader to
fade a sound out completely.
The Joemeek Digital Audio Interface provides high quality digital
audio outputs plus the ability to synchronize to an external word
clock. The digital audio outputs are compatible with most digital
recorders, as well as Digital Audio Workstations and mixers.
S/PDIF format is available from the optical and RCA Phono
connectors, while the transformer coupled XLR connector
provides a balanced, AES3 compatible output.
CONNECTORS
Two outputs are provided, jack and XLR, so you can
simultaneously feed (say) a recorder and a monitor amplifier. The
switch adjacent to the 1/4" jack selects the output operating level
to either +4dBu (suits most professional studio equipment) or
-10dBv (suits semi-pro or hi-fi equipment). The XLR output is
always +4dBu. Check with the handbook for whatever you are
feeding, to find out which level is required.
Highly stable onboard master clocks give low-jitter, hi-fi results.
Internal sample rates of 44.1kHz, 48kHz, 88.2kHz or 96kHz are
selected by means of rear panel switches. 44.1kHz is the
standard used for audio CD's, while 48kHz and 96kHz are widely
used in recording studios. In general, the higher the sample rate,
the better the audio fidelity, but the more disk space is required for
the recording. For example, recording at 96kHz requires twice as
much storage as 48kHz. Consult the manual of your recorder or
DAW as to what sample rates it will accommodate.
The XLR output is balanced and wired as follows:
Pin 2: + (hot)
Pin 3: - (cold)
Pin 1: ground
Alternatively the twinQ2 may be set to the frequency of an
external master word clock, generated, for example, by the
studio's recorder or DAW. When connected to the BNC socket
provided, a suitable external word clock will be detected
automatically and will override the twinQ2's internal word clock.
The jack output is balanced and wired as follows:
Tip: + (hot)
Ring: - (cold)
Sleeve: ground
Balanced or Unbalanced
The front panel LED labeled 'EXT CLK' illuminates when the
twinQ2 is successfully locked to an external word clock.
To run the XLR output unbalanced, it will be necessary to ground
pin 3 of the cable connector.
To avoid distortion, care should be taken not to overdrive the input
to the Digital Interface. The red LED next to the Output Gain
control is labeled "PEAK FSD" which stands for "Full Scale
Digital". Occasional flashes are OK but if it is on all the time, turn
something down!
To run the 1/4" jack output unbalanced, just plug in a mono jack
plug. Either way, this increases the gain of the "+" signal by 6dB,
so there is no drop in level compared with balanced gear.
All outputs on all Joemeek "Q2" series products are properly
balanced, which is to say there is a signal on both pins! In this way
the maximum possible common-mode rejection of interference,
can be achieved at the receiving end.
12
Using the twinQ2
Using the Compressor
GETTING CONNECTED
Start with the Compressor and Meequalizer off and adjust
'INPUT GAIN' and 'OUTPUT GAIN' so that the VU Meter reads
around 0dB. Now switch the meter to read gain reduction using
the 'GR' switch.
The figure shows the twinQ2 being used instead of a mixing desk
in a recording setup:
Set 'COMPRESSION' and 'ATTACK' fully anti-clockwise, with
'SLOPE' and 'RELEASE' at mid-position. Press the Compressor
'ON' switch and turn up the 'COMPRESSION' control until the
compressor GR meter starts to read 3dB or 5dB on audio peaks.
You should now be able to hear the compressor working as the
volume diminishes. Use the 'MAKE UP GAIN' control to restore
the signal to its previous (uncompressed) level. Alter the 'SLOPE'
control and listen to how the severity of the gain reduction
changes. Try changing the 'ATTACK' control and listen for
percussive sounds getting louder. Reducing the Attack and
Release times should emphasise this even more and the
compressor should start to "pump" audibly.
The overall result of compression depends on the combined
settings of the 'COMPRESS', 'SLOPE', 'ATTACK' and
'RELEASE' controls. Experiment with different combinations to
discover what best suits the material you wish to compress.
Watch the GR meter and don't overdo things - it's possible to
apply 20dB of gain reduction before you realise it!
Use the Compressor 'ON' switch to make comparisons between
compressed and uncompressed signals.
• A microphone is connected to the Mic Input
• A guitar is connected to the Instrument Input
Using the Meequalizer
• The insert point is being used to divert the preamplified
signal through an external effects processor
Always start with the Meequalizer boost/cut controls ('LF', 'MID'
and 'HF') set to "0" (the control knobs set vertically, in their centre
notches). This setting is also known as "flat".
• The XLR Output is connected to the recorder input
• The recorder output is connected to the Line Input for
playback. Previously recorded tracks may also be replayed
via the Line Input, to permit compression and equalization
You need to be careful about too much boost or "lift", since
boosting takes the twinQ2 closer to overload. The twinQ2 has
generous overload margins but when a lot of boost is used, it may
be necessary to compensate by reducing the 'OUTPUT GAIN' or
the 'INPUT GAIN' controls (the latter could affect the
'COMPRESS' setting though).
POWER SUPPLY
Connect the twinQ2 power cord to the AC connector on the rear
panel and switch on the mains supply. NB: ensure that the twinQ2
is set to the correct mains voltage for your region either 115V or
230V. Orientate the fuse holder / mains voltage selector draw so
that the required voltage appears at the top. If in doubt consult a
competent engineer.
Keep an eye on the VU Meter when adjusting the EQ. When the
red LED (labeled "PEAK FSD") lights, the twinQ2 is within 6dB of
clipping. Occasional flashes are OK but if it is on all the time, turn
something down!
The way to use the 'MID' control, is to apply quite a lot of boost,
then sweep the frequency until you "tune in" to the sound you are
interested in. Once you find it, adjust the amount of boost or cut to
give the desired effect.
Using the Preamp
Turn the 'INPUT GAIN' control to minimum and connect the input
source. If you are using a condenser microphone, remember to
press the '48V' Phantom Power switch. Set the 'OUTPUT GAIN'
to "0dB". Turn up the 'INPUT GAIN' until the microphone sound
registers on the VU Meter, adjusting it so that the meter reads
between "0" and "+3" on sound peaks. When the red LED
(labeled 'PEAK') lights, the twinQ2 is within 6dB of clipping.
Occasional flashes are OK but if it is on all the time, turn the
'INPUT GAIN' down! Remember you can check the preamp gain
at any time by pressing the 'METER PRE' switch.
Experiment with combinations of settings of EQ and try to picture
how the audio signal is being affected. Use the EQ 'ON' switch to
make comparisons between EQ'd and non-EQ'd signals.
13
Using the Output Stage
Troubleshooting
Final adjustments to the output level can be made with the
'OUTPUT GAIN' control, again keeping an eye on the VU meter
and 'PEAK FSD' LED. Note how this control can also be used to
fade out the signal completely.
1) No Power (no lights work)
• Is the power supply plugged in (both ends)?
• Is the mains power on?
• Is the mains voltage set correctly for your region?
• Has the mains fuse blown?
2) The microphone doesn't work
• Is it connected to the XLR input on the front or rear panel?
• If a condenser microphone, is the phantom power switched on?
• Is the 'LINE' switch out (LED off)?
• Is the 'INPUT GAIN' control turned up?
• Is the 'OUTPUT GAIN control turned up?
• Is something plugged in to the 'INSTRument' jack?
3) The line input doesn't work
• Is the source connected to the correct (jack) input on the rear?
• Is the 'LINE' switch in (LED on)?
• Is the 'INPUT GAIN' control turned up?
• Is the 'OUTPUT GAIN' control turned up?
• Is something plugged in to the 'INSTRument' jack?
4) The compressor doesn't work
• Is the Compressor 'ON' switch in (LED on)?
• Is the 'COMPRESS' control turned up enough?
• Is the 'SLOPE' control turned up enough?
• Is there enough signal, as set by the 'INPUT GAIN' control, to
drive the compressor?
5) Too little or too much compression
• Turn the 'INPUT GAIN' control up or down respectively, to adjust
the signal level to the compressor
6) The Meequalizer doesn't work.
• Is the EQ 'ON' switch in (LED on)?
• Is 'INPUT GAIN' control turned up?
• Is 'OUTPUT GAIN' control turned up?
7) Too much noise
• Is the 'INPUT GAIN' control too high? Try moving the mic closer
to the source
• Is the 'OUTPUT GAIN' control set too high (for example when
lots of compression is being used)?
• Is there too much EQ boost?
• Is the noise already present in the input signal? (Try removing
the input)
8) Sounds distorted
• Is the 'INPUT GAIN' control too high?
• Is the 'OUTPUT GAIN' control too high?
• Is there too much EQ boost?
• When using the Compressor, is the 'RELEASE' control set too
low?
14
Technical Specification
Input impedances
Mic: 1.2kohm; Line: 20kohm;
Pre-amp overall gain
18dB to 60dB (variable)
Notes
Instrument: 2.2Mohm
Common mode rejection
70dB
Equivalent input noise
-127.5dBu (unweighted)
Distortion
0.001% (below Compressor threshold)
Frequency response
15Hz to 70kHz (-3dB)
Maximum input before
clipping
Mic: +24dBu; Line: +45dBu
Headroom before clipping
+24dBu
Pad
20dB attenuation
High Pass Filter
12dB per octave cut below 80Hz
Compressor threshold
-6dBu to +22dBu (variable)
Compressor ratio
1:1 to 10:1 (variable)
Compressor attack time
1 msec to 100 msec (adaptive)
Compressor release time
0.1 sec to 3 sec (adaptive)
EQ Boost and Cut
±15dB (bell response)
EQ "Q"
0.9 (1.6 octaves)
LF Frequency
40Hz to 650Hz variable
MID Frequency
300Hz to 5kHz variable
HF Frequency
6kHz/12kHz switchable
Nominal output levels
+4dBu/-10dBv
Output impedance
100 ohm
Output Level switch
12dB attenuation
Noise Floor
-85dBu (typical, with ~40dB mic gain)
VU Meter
Analogue movement
Power supply
115V / 230V ac mains, 50/60Hz
Power consumption
30W
Mechanical
482W x 88H x 220D (overall)
Weight
3 kilos
Digital Interface
Resolution:
24-bit oversampled* delta sigma
Dynamic range:
typically 95dB A-weighted
Noise Floor:
typically 92dB A-weighted (referenced
to 0dBFS = +18dBu). So for a +4dBu
signal, the SNR is 78dB
Distortion (20Hz - 20kHz):
0.01% @ 0dBu at 96kHz sample rate
0.02% @ 0dBu at 48kHz sample rate
0.02% @ -1dBFS at all sample rates
Crosstalk:
typically -67dB (20Hz - 20kHz)
* 20kHz bandwidth sampled at 96kHz = 2.4x
Master clock frequency / sample rate = 256x at 96kHz
15
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